1. Field of the Invention
This invention relates generally to imaging systems and, more specifically, to a low cost system for creating scanned images of documents.
2. Background Information
Several devices are currently available for scanning documents. Flat bed scanners, for example, are routinely used to generate a digital, electronic version of a hard copy of a document. Flat bed scanners typically employ a scanning mechanism disposed below a glass plate. A document to be scanned is placed face-down on the glass plate. Light is projected onto the document and the reflected light from the document is focused by a lens onto light-sensitive diodes. The diodes translate the reflected light into electrical currents. An analog-to-digital (A/D) converter converts the electrical currents into digital pixels. The pixels are then processed by a graphics or optical character recognition program to produce an electronic version of the scanned document.
Hand-held scanners are also commercially available for creating digital, electronic versions of documents. Hand-held scanners work in a similar fashion as flat-bed scanners, although the operative area is typically much smaller. In particular, a hand held scanner includes one or more light emitting diodes (LEDs) that illuminate the document. The reflected light from the document is focused by a lens onto a charge coupled device (CCD) which contains a series of light detectors. An A/D converter generates digital pixels from the output of the CCD's light detectors.
Although the prices of flat-bed and hand-held scanners continues to fall, they are still relatively expensive. Flat bed scanners, moreover, can be relatively bulky. Accordingly, they are not considered to be portable equipment. For people who frequently travel, flat bed scanners are not a suitable method of scanning documents. Although hand-held scanners are relatively portable, they typically produce poorer quality images than flat bed scanners. Most hand-held scanners, moreover, are not wide enough to scan common document sizes, such as those on 8½ by 11 inch paper.
Hewlett-Packard Co. of Palo Alto, Calif. recently released a hand-held scanning product called Capshare. Although its scanning area is only four inches wide, according to the product literature, it can “stitch” together sections to form a single image of larger sized documents, e.g., 8½ by 14 inches. The Capshare product, however, is limited to generating bi-tonal images of scanned documents, and is relatively expensive. It is also extremely sensitive to perturbations in device-to-document separation.
Other products for stitching together images also exist. QuickStitch software from Enroute Imaging, for example, stitches individual digital photographs into a single, panoramic image. Other software-based products include Panorama from Picture Works Technology, Inc., now Internet Pictures Corporation. However, neither Quickstitch nor Panorama can reliably generate a composite image of a document containing text.
Accordingly, a need exists for a low-cost system for creating digital, electronic versions of documents containing text.